A search for a heavy resonance decaying into a top quark and a W boson in proton-proton collisions at $\sqrt{s} =$ 13 TeV is presented. The data analyzed were recorded with the CMS detector at the LHC and correspond to an integrated luminosity of 138 fb$^{-1}$. The top quark is reconstructed as a single jet and the W boson, from its decay into an electron or muon and the corresponding neutrino. A top quark tagging technique based on jet clustering with a variable distance parameter and simultaneous jet grooming is used to identify jets from the collimated top quark decay. The results are interpreted in the context of two benchmark models, where the heavy resonance is either an excited bottom quark b$^*$ or a vector-like quark B. A statistical combination with an earlier search by the CMS Collaboration in the all-hadronic final state is performed to place upper cross section limits on these two models. The new analysis extends the lower range of resonance mass probed from 1.4 down to 0.7 TeV. For left-handed, right-handed, and vector-like couplings, b$^*$ masses up to 3.0, 3.0, and 3.2 TeV are excluded at 95% confidence level, respectively. The observed upper limits represent the most stringent constraints on the b$^*$ model to date.
We present a measurement of the ratio σB(W→eν)σB(Z0→e+e−) in p¯p collisions at s=1.8 TeV The data represent an integrated luminosity of 21.7 pb−1 from the 1992-1993 run of the Collider Detector at Fermilab. We find σB(W→eν)σB(Z0→e+e−)=10.90±0.32(stat)±0.29(syst). From this value, we extract a value for the W width, Γ(W)=2.064±0.061(stat)±0.059(syst) GeV, and the branching ratio, Γ(W→eν)Γ(W)=0.1094±0.0033(stat)±0.0031(syst), and we set a decay-mode-independent limit on the top quark mass mtop>62 GeV/c2 at the 95% C.L.
We present the results of a search in p¯p collisions at s=1.8 TeV for the top quark decaying to a charged Higgs boson (H±). We search for dilepton final states from the decay chain tt¯→HH (or HW, or WW) + bb¯→ll+X. In a sample of 19.3 pb−1 collected during 1992-93 with the Collider Detector at Fermilab, we observe 2 events with a background estimation of 3.0 ± 1.0 events. Limits at 95% C.L. in the (Mtop,MH±) plane are presented. For the case Mtop<MW+Mb, we exclude at 95% C.L. the entire (Mtop,MH±) plane for the branching ratio B(H→τν) larger than 75%. We also interpret the results in terms of the parameter tan β of two-Higgs-doublet models.
We present a measurement of $\sigma \cdot B(W \rightarrow e \nu)$ and $\sigma \cdot B(Z~0 \rightarrow e~+e~-)$ in proton - antiproton collisions at $\sqrt{s} =1.8$ TeV using a significantly improved understanding of the integrated luminosity. The data represent an integrated luminosity of 19.7 pb$~{-1}$ from the 1992-1993 run with the Collider Detector at Fermilab (CDF). We find $\sigma \cdot B(W \rightarrow e \nu) = 2.49 \pm 0.12$nb and $\sigma \cdot B(Z~0 \rightarrow e~+e~-) = 0.231 \pm 0.012$nb.
We present the first measurement of associated direct photon + muon production in hadronic collisions, from a sample of 1.8 TeV $p \bar p$ collisions recorded with the Collider Detector at Fermilab. Quantum chromodynamics (QCD) predicts that these events are primarily from the Compton scattering process $cg \to c\gamma$, with the final state charm quark producing a muon. Hence this measurement is sensitive to the charm quark content of the proton. The measured cross section of $29\pm 9 pb^{-1}$ is compared to a leading-order QCD parton shower model as well as a next-to-leading-order QCD calculation.
This paper presents the first direct measurement of the $B$ meson differential cross section, $d\sigma/dp_T$, in $p\overline{p}$ collisions at $\sqrt{s}=1.8$ TeV using a sample of $19.3 \pm 0.7$ pb$~{-1}$ accumulated by the Collider Detector at Fermilab (CDF). The cross section is measured in the central rapidity region $|y| < 1$ for $p_T(B) > 6.0$ GeV/$c$ by fully reconstructing the $B$ meson decays $B~{+}\rightarrow J/\psi K~{+}$ and $B~{0}\rightarrow J/\psi K~{*0}(892)$, where $J/\psi \rightarrow \mu~+\mu~-$ and $K~{*0} \rightarrow K~+ \pi~-$. A comparison is made to the theoretical QCD prediction calculated at next-to-leading order.
We have used 19 pb**-1 of data collected with the Collider Detector at Fermilab to search for new particles decaying to dijets. We exclude at 95% confidence level models containing the following new particles: axigluons with mass between 200 and 870 GeV, excited quarks with mass between 80 and 570 GeV, and color octet technirhos with mass between 320 and 480 GeV.
We present the first observation of the all hadronic decay of tt¯ pairs. The analysis is performed using 109pb−1 of pp¯ collisions at s=1.8TeV collected with the Collider Detector at Fermilab. We observe an excess of events with five or more jets, including one or two b jets, relative to background expectations. Based on this excess we evaluate the production cross section to be in agreement with previous results. We measure the top mass to be 186±10±12GeV/c2.
We have searched for heavy neutral gauge bosons (Z′) in dielectron and dimuon decay modes using 110pb−1 of p¯p collisions at s=1.8TeV collected with the Collider Detector at Fermilab. We present a limit on the production cross section times branching ratio of a Z′ boson decaying into dileptons as a function of Z′ mass. For mass MZ′>600GeV/c2, the upper limit is 40 fb at 95% confidence level. We set the lower mass limits of 690, 590, 620, 595, 565, 630, and 600GeV/c2 for ZSM′, Zψ, Zη, Zχ, ZI, ZLR, and ZALRM, respectively.
We have measured the fraction of J/ψ mesons originating from χc meson decays in pp¯ collisions at s=1.8TeV. The fraction, for PTJ/ψ>4.0GeV/c and |ηJ/ψ|<0.6, not including contributions from b flavored hadrons, is 29.7%±1.7%(stat)±5.7%(syst). We have determined the cross sections for J/ψ mesons originating from χc decays and for directly produced J/ψ mesons. We have found that direct J/ψ production is in excess of the prediction of the color singlet model by the same factor found for direct ψ(2S) production.
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